resizewin: Stop printing bogus NUL to TTY

A char array has an implicit NUL terminating it, which sizeof will
include, so we need to subtract 1 here. Printing a NUL can cause issues
for things like CI environments that aren't expecting it, especially
with recent Jenkins being stricter about not putting NUL in XML files.

Fixes:		3d222369ac ("Add a small tool, resizewin(1), to query terminal for window size")
MFC after:	1 week

usr.bin/resizewin/resizewin.c

@@ -101,7 +101,7 @@ main(int argc, char **argv)
 	if (tcsetattr(fd, TCSAFLUSH, &new) == -1)
 		exit(1);
 
-	if (write(fd, query, sizeof(query)) != sizeof(query)) {
+	if (write(fd, query, sizeof(query) - 1) != sizeof(query) - 1) {
 		error = 1;
 		goto out;
 	}